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Java > Open Source Codes > org > apache > bcel > classfile > ConstantClass


1 /*
2  * Copyright 2000-2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  *
16  */
17 package org.apache.bcel.classfile;
18
19 import java.io.DataInputStream JavaDoc;
20 import java.io.DataOutputStream JavaDoc;
21 import java.io.IOException JavaDoc;
22 import org.apache.bcel.Constants;
23
24 /**
25  * This class is derived from the abstract
26  * <A HREF="org.apache.bcel.classfile.Constant.html">Constant</A> class
27  * and represents a reference to a (external) class.
28  *
29  * @version $Id: ConstantClass.java 386056 2006-03-15 11:31:56Z tcurdt $
30  * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
31  * @see Constant
32  */
33 public final class ConstantClass extends Constant implements ConstantObject {
34
35     private int name_index; // Identical to ConstantString except for the name
36
37
38     /**
39      * Initialize from another object.
40      */
41     public ConstantClass(ConstantClass c) {
42         this(c.getNameIndex());
43     }
44
45
46     /**
47      * Initialize instance from file data.
48      *
49      * @param file Input stream
50      * @throws IOException
51      */
52     ConstantClass(DataInputStream JavaDoc file) throws IOException JavaDoc {
53         this(file.readUnsignedShort());
54     }
55
56
57     /**
58      * @param name_index Name index in constant pool. Should refer to a
59      * ConstantUtf8.
60      */
61     public ConstantClass(int name_index) {
62         super(Constants.CONSTANT_Class);
63         this.name_index = name_index;
64     }
65
66
67     /**
68      * Called by objects that are traversing the nodes of the tree implicitely
69      * defined by the contents of a Java class. I.e., the hierarchy of methods,
70      * fields, attributes, etc. spawns a tree of objects.
71      *
72      * @param v Visitor object
73      */
74     public void accept( Visitor v ) {
75         v.visitConstantClass(this);
76     }
77
78
79     /**
80      * Dump constant class to file stream in binary format.
81      *
82      * @param file Output file stream
83      * @throws IOException
84      */
85     public final void dump( DataOutputStream JavaDoc file ) throws IOException JavaDoc {
86         file.writeByte(tag);
87         file.writeShort(name_index);
88     }
89
90
91     /**
92      * @return Name index in constant pool of class name.
93      */
94     public final int getNameIndex() {
95         return name_index;
96     }
97
98
99     /**
100      * @param name_index the name index in the constant pool of this Constant Class
101      */
102     public final void setNameIndex( int name_index ) {
103         this.name_index = name_index;
104     }
105
106
107     /** @return String object
108      */
109     public Object JavaDoc getConstantValue( ConstantPool cp ) {
110         Constant c = cp.getConstant(name_index, Constants.CONSTANT_Utf8);
111         return ((ConstantUtf8) c).getBytes();
112     }
113
114
115     /** @return dereferenced string
116      */
117     public String JavaDoc getBytes( ConstantPool cp ) {
118         return (String JavaDoc) getConstantValue(cp);
119     }
120
121
122     /**
123      * @return String representation.
124      */
125     public final String JavaDoc toString() {
126         return super.toString() + "(name_index = " + name_index + ")";
127     }
128 }
129
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